Crank pin grinder



Sept. 3o, 1941. G. pRiLL 2,257,619

CRANK PlN GRINDER Filed Nov. 24, 1959 2 Sheets-Sheet l ATTOR N EY.

Patented Sept. 30, 1941 CRANK PIN GRINDER George Ferdiend Prill, Jamestown, N. Dak., as-

signor to Goetz-Voss Corporation, Wauwatosa,

Wis.

Application November 24, 1939, serial No. 305,805v 20 Claims. (101.51-241) `lVIy invention relates in` general to improvements inthe art of dressing or finishing cylindrical machine elements, and relates more specifically to improvements in the construction` and operation of portable grinders for locomotive crank pins or the like.

Generally dened an object of my invention is to provide an improved pin grinder for locomotive driving crank pins or the like, which is simple and durable in construction, and which is also readily manipulable and highly efficient in use.

`'Ihe driving crank pins for locomotives, especially in the mountain districts, are subject to rather rapid wear and must therefore be dressed from time to time in order to cooperate properly with the connecting rods. Since these pins are firmly attached to the heavy and massive drive wheels, and the latter are likewise frmlyattached to the axles, it would be an extremely tedious and prolonged task toeven attempt to remove the crank pins for re-dressing in a `lathe or stationary grinder, and such procedure would be highly objectionable and far too costly because it would keep the locomotives inactive for too long a period of time. This work must therefore be accurately accomplished as quickly as possible, and without necessity of removing either the pins or the wheels.` While various types of tools have heretofore been used for the purpose of dressing locomotive crank pins, including portable crank-pin turning machines which are adapted to `be attached directly to the pins and suspended therefrom during the cutting operation, these prior devicesare all ob- 1,

jectionable` either because they are too slow in action, they lack necessary accuracy in performance, they are too awkward and diflicult to operate, or they are too costly.

It is therefore a more specic object of my invention to provide a new and useful portable grinder especially adapted to re-finish worn locomotive crank pins, and which may be suspended directly from thepin ends during the grinding operation, thereby avoiding necessity of disturbing the locomotive assemblage except for removal of the connecting rods which normally coact with the worn pins.

Another specific object of this invention is to provide an extremely simple and relatively inexpensive portable grinder assemblage which can be quickly applied to and detached from a crank pin or the like, and which requires no high degree of skill for operation.

A further specific object of my present invenr tion is to provide an improved crank pin dressingor finishing machine which is adapted for eiective cooperation with pins of various sizes and types, and which may be conveniently suspended from various styles of crank pins.

Still another specific object of theinvention is to provide an improved portable pin grinder which meets all requirements of railroad maintenance as to low cost, time saving, labor saving, and accuracy, and which may be utilized to grind diversev circular pins and bored holes, such as crank pins, trailer journals, car journals,` connecting rod bores, cylinder head seats, or the like. l

An additional specific object of this invention is to provide an improved revolving grinder which is revolvable about and movable along the central axis of the cylindrical surface being ground, and which may be quickly and accurately adjusted to vary the out.

Another specific object of the present invention is to provide a sturdy portable grinder unit which may be manufactured and sold at relatively moderate cost, and which is adapted for many different uses.

These and other specific objects and advantages of my invention will be apparent from the followingdetailed description.

A clear conception of `embodiments of the` various features constituting my present invention, and' of the mode of constructing and ci` utilizing crank pin grinders built in accordance with the improvement, may be had by referring to the drawings accompanying and forming a partof this specification wherein like reference characters designate the same or similar parts in the various views.

1 Fig. 1 is a perspective view of one of the improved portable orank pin grinders, showing the same suspended from a locomotive driving crank pin and ready for operation;

` Fig. 2 is an' enlarged central longitudinal section through 'one of the portable grinders, show` ing themechanism for suspending the unit from one type of crank pin;

Fig. 3 is a transverse cross-section through the portable grinder of Fig.` 2, taken along the line 3 3;

Fig.` 4 is a similar transverse cross-section taken through the portable grinder of Fig. 2, the section being taken along the line 4-4;

Fig. 51is a 'fragmentary side view of the mechanismfor operatively `connecting the grinding wheel carrier to the feed screw, showing the mechanism in active position;

Fig. 6 is a transverse section through the mechanism of Fig. 5, taken along the line 6 6;

Fig. 7 is a fragmentary side View similar to that of Fig. 5, but showing the connecting mechanism in inactive position;

Fig. 8 is a fragmentary central longitudinal section through a portion of the grinding assemblage, showing the mode .of attaching the same to a crank pin of a type different fromthat shown in Fig. 2,; and

Fig. 9 is another fragmentary central longitudinal section through a similar portion of the grinder assemblage, showing the mode of attach.- ing the same to still another type of crank pin.

While I have shown and specifically described the invention as being especially applicable for the purpose of dressing various types of locomotive crank pins, it is not the intent to thereby unnecessarily restrict the scope or utility of the, improvement, and the assemblage may and has been used for diverse other purposes such as grinding trailer and car journals,A and bored holes. The term .crank pin as used herein should therefore be given the broadest possible interpretation; and while the grinding units of the assemblage specically illustrated herein are operable by rotary compressed-air driven motors, these may also be replaced by electric motor driven units or the like.

Referring to the drawings, the improved as semblage as illustrated in Fig. l, isa machine which has been in successful commercial operation for some time, while the assemblages shown in Figs. 2 to 9 inclusive disclose somewhat refined details of construction, but the essential-elements of the two assemblages while being slightly different in design, function the same and Will be referred to with like reference characters.

'Ihe improved assemblage comprises in generalv an elongated central shaft I3 havingone end II screw threaded for either direct or indirect, but firm attachment to a crank pin I2, and having its opposite free end I3 provided with a suitable feed thread; an elongated tubular support I4 loosely embracing the shaft I between the threaded ends II, I3, and coacting with a socket member I5 which may snugly engage the reduced outer end I 6 of a crank pin I2; a sleeve member or drum I'I rotatably journalled upon the tubular support I4 by means of spaced roller bearings I8 which are readily attachable to and detachable from the overhanging end of the pin I2, may be either attached directly to the pin end as in Fig. 2, or through adapters as in Figs. 8 and 9. In Fig. 2, the crank pin I2 has a threaded socket with which the shaft end II directly coacts, and the socket member I5 which snugly embraces the overhanging pin end I3, coacts with a flange 3l formed integral with the tubular support I, and both the support III and socket member I5 are rmly clamped in position by a nut 32 threaded on the shaft I3 and engaging an adjustable collar 33thr'eaded on the outer end of the tubular supsupport It must be attached to the pin I2 in line with its axis, by means of a. special adapter cornformed to prevent relative axial shifting of the y drum I'I and support I4; a ring orY collar I9 revolvable with and slidable along the drum I'I, and carrying diametrically opposite brackets 2i) in which four parallel guide elements or rods 2|, 22 areiixedly but adjustably supported; a steadying ring or plate 23 rigidly interconnecting the ends of the rods 2I 22, and being bored to i'lt the adjacent portion of the crank pin I 2; air pressure operated grinder units 24 swingably adjustably suspended Vfrom the diametrically opposite guiding rods 2I and having rotary grinding wheels 25 which are cooperable with the peripheral surfaces of the crank pin I2; mechanism including levers 26, threaded spindles 2'I and cranks 28 for adjusting the grinder units 24 toward and away from the crank pin periphery about the axes of the guide rods 2 I; and a releasable clamp 29 Yand connecting rods 30 for attaching the grinder units 24 to the feed screw end I3 of the fixed shaft I3 through the collar I9 and guide rods 2|, 22.

The crank pins I2, I2', I2" may be of various types as shown in Figs. 2, 8 and 9, and the shaft ID which should in each case be mounted approximately concentric with the crank pin axis, and, be

prising a spindle 34, a coupling sleeve 35, a spacer block 36, and a filler block 3l. The spindle-34 has one end threaded for rm attachment to a central threaded socket in the pin I2', and the coupling sleeve 35 coacts with the opposite threaded end of the spindle 33 and with the threaded end .II of the feed-shaft Iii, so as to provide arigid support for the shaft Ill approxi-l mately in line with the crank pin axis. -The spacer block 35'eng'ages the end surface ofthe crank pin I2 and has an end projection fitting a bore in the filler block 31, and the latter snugly embraces the spindle 33 and is snugly embraced by the socket member I5 which coacts with the flange 3I of the supportv I4. The support I4,

flange 3l, .block 3'I Vand block v33 are clampedV against the pin end by a nut 32 as in Figgz.

In Fig.` 9, the crank pin I2 is hollow and has no threaded end socket disposed centrally thereof. There is however an eccentric `end socket threaded to nt the grease injector, and I have provided a special adapter comprising a cap screw 38, an adapter socket 39, and a connecting block 40 for effecting central attachment of the shaft I0 and support I4 to such crank pins I2. The adapter socket 39 of this assemblage ts snugly within the central end recess of the pin I2 and may be firmly confined within this recess by meansof the eccentric cap screw 38. The socket 39 has internal screw threads formed concentric with the crank pin axis, and with which external screw threads on the block 40 coact, and this block I3 has a threaded socket adapted'for reception-of the shaft end II. The alining socket member I 5 coacts with the reduced pin end I6 and with the support ange 3|, as previously described, and these parts may be clamped together by means of a nut 32, as in Fig. l. The support I4 may be provided with an end recess 4I for the reception of this adapter, and additional special adapters may be provided for other types of crank pins.

The rotary member or drum Il should be freely rotatable with minimum effort, about the central axis of the crank pin I2, and the support I4 and roller bearings IS provide for such rotation. While the bearings I 3 are of the inclined roller type, any suitable type of anti-friction bearing which' will prevent displacement of the drum I'I along its axis, may be utilized. The collar 33 and nut 32 may be concealed within the end of the drum Il, nbut the interior of the drum should not actually touch the collar 33 so that free rotation of the drum might be Vinterfered with. The elongated collar. or ring I9Vis split as shown in Figs. 2 and 4, so that? this ring I9 may be moved longitudinally ofythe drum I1, and may be adjusted toeliminate Vexcessive clearance by meansof the 'clamping screws 42-. The collar I9 is provided with oppositely disposed recessed lugs 43 with which spacer blocks 44 coact, and the brackets 29 are-rigidly attached to the split collar by means of bolts `45 piercing the blocks 44 and screwed into the'lugs 43.l Each bracket has bored holes with which the guide rods 2|, 22Acoact, and the brackets 29 are preferably rigidly interconnected by meansH of links 46 shown in Fig. 4, in order to 'maintainA the guide rods 2|, 22 in parallel position. `The guide rods 2|, 22 are also rigidly 'interconnected and maintained parallel to` each other`by theend plate 23 which'bears upon the fcrankpin I2 and is rotatable about the Vcrank ypinaxis when the drum I1 is rotated and therods `2I,` 22 are revolved.

The guide rods 2|,'22 are rotatably adjustable Within the brackets 29 and plate 23, and may be locked in adjusted position with the aid of set screws 41. Each of the rotary air pressure operated grinder units 24 is suspended from the adjacent guide rod 2| by means of a supportingV bracket 48 as shown in Figs. 2 and 3, and may be adjusted along and around its suspension rod 2| and clamped in adjusted position with the aid of clamping screws 49. When the units 24 have been adjusted and clamped to the guide rods 2|, they may be` revolved and moved longitudinally with these rods to cause the `grinding wheels 25 to revolve about and `move along the crank pin I2. The units 24 may, however, be moved independently of eachother, toward and away from the crank pin periphery, in order to vary the cut and as illustrated in dot-and-dash lines in Fig. 3, with the aid of the adjusting mechanism shown in Fig. 4. The levers 26 are rigidly attached to the grinder carrying rods 2|, soithat whenthe set screws 41 are released, swinging of the' levers 26 will cause the rods 2| to rotate about their own axes relative to the carrier brackets 20 and plate 23. The screw spindles 21 arethreaded `for adjustment in pivot blocks 59 swivelled in the swinging ends of` the levers 26, and coact with the other guide rods 22, so that when the cranks 28 are manipulated, the levers 26 will be swung about the axes `of the rods 2| and will rotate these rods to thereby cause the grinding units 24 to swing about the rod axes toward or away from the crank pin I2, depending upon the direction of -rotation of the cranks 28. This swinging adjustment of the grinder units provides avery ne andaccurate adjusting means for varyingthe degree of grinding, by virtue of the length of the levers 26 and the fact that thelever movement can, be readily controlled with the ne screwthreads on the spindles 21, and quicker but less accurate adjustment of the units 24 is made possible witlrthe aid of the clamping screws 49.

The grinder units 24 are preferably of similar and interchangeable construction,` and have rotary air or electric motors I which are adapted to be detachably clamped to the brackets 48 in l any suitable manner, and the grinding `wheels 25 are adapted to be driven at high speed by the motors 5I. The wheels 25 may be provided with guards 52, and when air motors`5| are utilized, the compressed air may be admitted to the motors 5| throughshortexible tubes 53 and a Y-pipe 54 connected to `an air supply hose 55 by means of a swivel joint 55,'see Fig. 1. This assemblage will permit the units 24 and their carriage to be slid along the drum I1 and revolved freely with the supporting collar I9 and drum|1 about the longitudinal axis of the crank pin I2 and support I4, and the Y-pipe 54 may be attached to the brackets 20, so that Ait will serve as a handle for sliding the collar I9 and for revolvingthe drum I1 and the associated parts.

The revolving structure including the collar I9 maybe moved along the drum I1 and the crank pin axis either by hand, or at auniform rate with the aid of the threaded' `shaft end I3. Such interchangeable operation is made possible by means of the releasable clamp 29 shown in Figs. 5 to '7 inclusive, and this clamp comprises the connecting rods 30 attached to the collar I9, and a pair of transverse bars or plates `51, 58 having screw threads cooperable with the shaft end I3, and which are secured to the ends of the rods 39. The plates 51, 58 are guided for movement toward and away from each other by pins 59 and are constantly urged apart Vby compression springs 60; `and a cam lever 6| which is swingably suspended from a U-bolt 62 secured to the plate 51, is operable to bring the plates 51, 58together and into operative 'coaction with the threaded shaft end I3 against the action of the springs 60. When the cam lever 6I is swungdown as in Fig. 5, the internal screw threads voftheV plates 51, 58 are in engagement with Athe threads of the shaft end I3, and are therefore active in advancing thecollar I9 and grinder units 24 at a uniform speed along the axis of the drum I1 and the crank pin I2, when the units '24 and drum I1 are revolved about this axis. When the cam lever 6I is swung up as in Fig. 7, the plates 51, 58 are released from engagement with the threaded shaft extension I3, and the collar I9 and grinder units 24 may then be moved freely along the crank pin axis at any desired and variable rate of speed. Either the rods 30 or the Y-pipe 54 may be utilized to manipulate the revolving and sliding structure of the machine. The crank pins I2, I2', I2 Vare normally rigidly attached to driving or driven wheels 63 or the like, and during operation of the locomotive, these crank pins have connecting rods coacting therewith in a well known manner.

`Vhile the normal use of my improved crank pin grinder should be clearly apparent from the foregoing detailed description, a short resume thereof will be given. When a locomotive has been pulled into the round-house or repair shop, the connecting rods will first be removed from the worn crank pins I2, after which the improved grinder assemblage may be mounted upon a worn pin.Y Depending upon the type of crank pin to which the assemblage is to be applied, an adapter such as shown in Fig, 8 or in Fig. 9 may be used or the shaft I0 may be directly attached to a crank pin I2 such as shown in Fig. 2. After the shaft IU has been properly attached to the crank pin, the support I4 with its associated elements may be applied to the shaft I0 and clamped in place by manipulation of the nut 32 and collar 33. The grinding wheels 25 may then be roughly adjusted and positioned by releasing the cap screws 49, and the collar I9 and rods 2|, 22 may be positioned to place the Wheels 25 within the zone of grinding, by releasing the cap screws 41 and shifting the collar I9 along the revolvable drum I'I.` When the proper initial adjustment has been thus effected, the grinding wheels 25 may be adjusted toward or away from the crank pin periphery with theV aid of the cranks 28 and the wheels 25 may be thus adjusted to make any desired depth of out. The lever SI may thereafter b'emanipulated to bring the clamp 29 into action, whereupon air may be admitted to the motors 5I through the supply pipe 55 to cause thegrinding wheels 25 to revolve. The revolving wheels 25 coacting with the crank pin periphery will tend to cause the motors 5| and guide rods 2l, 22 to revolve about the crank pin axis together with the'collar I9 and this-revolution of the partswill cause the screw threads on the shaft end I3 to gradually advance the collar I9 and the parts associated therewith along the revolving drum I'I and will thus advance the revolving wheels 25 along the periphery of the pin I2. .The action of the grinding wheels 25 may be aided manually by Vutilizing the Y-pipe 54 or the rods 35 as handles, and the screw threads on the shaft ID will necessarily control the rate of lateral advancement of the wheels 25 along the crank pin axis, while the rate of revolution of the wheels about the pin axis will regulate the rate of grind- Y ing or movement of the wheels 25 about the crank pin. By releasing the 'clamp 29, the rate of ad- Vancement of the wheels 25 along the crank pin I2 may be materially increased, and when one surface of the pin has been nished,the collar I9 may be shifted to permit finishing of other portions of the crank pin.

It will thus be apparent that my invention provides an improved grinding assemblage which will permit rapid and accurate dressing of worn crank pins, without removing the pins from their driving wheels 63 or other supports. The revolving drum I'I by virtue of its mounting on antifriction bearings I8, may be freely rotated about the crank pin axis, and the collar I9 which is rotatable with the drum l1 about this axis, is also freely slidable along the drum so as to shift the wheels 25 along the cylindrical crank pin surface. The ring 23 'cooperates with the brackets 20 to maintain the'guide rods 2 I, 22 in parallel position, so that the axes of rotation of the grinding Vwheels will always remain parallel to the central axis of the crank pin. The adjusting mechanism for revolving the grinder units 24 about the axes of their suspension rods 2|, permits very ne and accurate adjustment of the positions of the wheels, and it has been found that rotation of the wheels 25 during normal operation of the unit, automatically causes the' collar I9 to move along the drum I'I due to the coaction of the clutch 29 with the screw threads of the shaft end I3. vThe assemblage may also be readily adjusted so as to cooperate with cylindrical surfaces of various lengths and diameters, and because of the fact that the improved grinding mechanism is supported solely by the crank pin I2 which is being ground, the unit may be readily centrallized with the supporting pin I2- The improved grinding unit has proven highly successful in actual commercial use in locomotive repair shops and it has been found that crank pins may be accurately renished with minimum delay in use of the locomotives. The entire assemblage may obviously be manufactured at moderate cost, is highly flexible in use, and may be manipulated by a novice.

It should be understood that it is not desired to limit this invention to the exact details of construction or to the precise rmode of use, herein shown and described, forY various modifications within the scope of the claims may occur to persons skilled in the art. V-

Iclaim: p 1. In combination, a feed shaft attachable to the overhanging end of a crank pin, a tubular support embracing said shaft and having a socket embracing the crank pin end, saidshaft ,havingv a threaded extension projecting beyondV the overhanging Vend of said support, a rotary drum journalled on said support, brackets suspended from said drum, guide rods carried Vby said brackets and extending parallel to the axis of rotation of said drum, grinder units suspended from said guide rods on opposite sides of the crank pin and being slidable along said drum, means for effecting adjustment of said vunits relative to the axes of said guide rods to move the grinding portions of said units toward or away from the crank pin periphery,rand means cooperable with said threaded shaft extension to move said grinder units longitudinally of the crank pin axis.

.2. In combination, an elongated support attachable to the overhanging end of a crank pin in axial alinement therewith, a rotary `drum journalled on said support and ,being fixed against axial displacement, guide rods carriedby said drum and being revolvable about the drum axis and freely slidable along the drum, grinder units suspended from said guide rods onopposite sides of the crank pin and being slidable along said drum, means for effecting adjustment of said units about the axes of said guide rods to move the grinding portions of said units toward and away from the crank pin periphery, and means coacting with said guide rods independently of said drum for effecting uniform movement of said grinder units longitudinally of the drum axis and of the crank pin when said guide rods are revolved.

3. In combination, an elongated support attachable to the overhanging end of a crankV pin, a drum rotatable upon said support and being fixed against axial displacement, a guide, rod carried by said drum and being revolvable about the drum axis during rotation of said drum, a grinder unit revolvablewith and vfreely slidable along said drum, means for effecting adjustment of said unit relative to said rod to move the grinding portion ofy said unit toward and away from the crank pin periphery, and means operable by the rotationV of said drum and coacting with said rods independently of the drum to move-said grinder unit along the drum and crank pin.

4. In combination, a support attachable to the overhanging end of a crank pin, a member freely rotatable upon said support about the crank pin axis but fixed against axial displacement and having a guide element slidable freely therealong and revolvable about said axis, a grinding wheel movable along said axis with said guide element, means for effecting adjustment of said Wheel toward and away from the crank pin'perpheiy,

and means operable by the rotation of said member and coacting with said element independently of the member for moving said grinding wheel along said rotatable member.

5. In combination, a support attachable tothe a `grinding wheel movable with` said guide element,Y and means operable by the rotation of said member and coacting with saidfelement inde- .pendently of the member ,for advancing said wheel alonglthe crank pin at a uniform rate.

.6. In combination, a support attachable to the .overhanging end of `a crank pin, a member rotatable aboutthe crank pin `axis and having a guide element slidable directly thereon and therealong and'revolvable about said axis, an anti-friction bearing between said support and said member, a grinding Wheel movable with said guide `element, vmeans for `electing adjustmentg of said wheel `toward and away from: the crank pin periphery, and means operable by the rotation of said member and coacting with said element independently of the member for advancing said wheel along the `crank pin at a uniformrate.'

7. AIn combination, a` support, means for. effecting interchangeable attachment of saidk support to the overhanging ends of crank pins of different types, a smooth cylindrical drum member rotatable upon said support and having a guide, element slidablygdirectly thereon parallel to and revolvable about the crank pin axis, a grinding wheel movable with said guide element,

and means operable by the rotation of said member and coacting with said element independently of the drum member for advancing said wheel along the crank pin at a uniform rate.

8. In combination, a support, means for effecting interchangeable attachment of said support to the overhanging ends of crank pins of different types, a smooth cylindrical drum member rotatable upon said support and having a guide element slidable directly thereon parallel to and revolvable about the crank pin axis, a grinding wheel movable with said guide element, means for effecting adjustment of said Wheel toward and away from the crank pin periphery, and means operable by the rotation of said member and coacting directly with said element for advancing said wheel along the crank pin at a uniform rate.

9. In combination, a support attachable to an endof a crank pin, a member rotatable about the crank pin axis but fixed against axial displacement and having diametrically opposite guiding elements slidably supported thereon and revolvable about said axis, a grinding wheel movable along said axis with each `of said guiding elements, said grinding wheels being disposed for peripheral engagement with the crank pin periphery on opposite sides of said axis, and means operable by the rotation of said wheels and coacting directly with said guiding element for advancingthe same longitudinally of said member and along the crank pin at a uniform rate. 10. In combination, a support attachable to an end of a crank pin, a member rotatable about the crank pin axis but fixed against axial displacement and having diametrically opposite guiding elements slidably supported thereon and revolvable about said axis, a grinding wheel movable along said axis with each of said guiding elements, said grinding wheels being disposed for peripheral engagement with the crank pin periphery on opposite sides of said axis, means for effecting adjustment of said grinding Wheels toward and away from the crank pin periphery, and means operable by the rotation of said wheels and coacting directly with said elements for advancing the same longitudinally of said member and along the crank pin at a uniform rate.

, 11. In combination, asupport formed lfor suspension from a crankpin inline with the crank pin axis, a drum rotatable upon said support and `being iixed against movement along said axis, a collar rotatable with andslidable directly upon and along said drum, guide rods carried by said collar, and grinding units suspended from said guide rods and being revolvable with and movable along saiddrum. 3

12. In combination, a support formed for suspension from a crank pin in line with the crank pin axis, a drum rotatable upon said support and being fixedagainst movement along said axis,ra c ollar rotatable :with and ,slidable along said drum guide rods` carried` by said collar, and grinding units suspended from said guide rods and being revolvable with andslidable directly upon and along said drum, said units being swingably adjustable about the axes of their suspension rods toward andaway from said crank pin.

13. In combination, a support formed for suspension froma crank pin in line with the crank vpin axis,` a smooth `cylindrical drum rotatable upon said support and being iixed against movement along said axis, anti-friction bearings interposed between said drum and said support, a collar rotatable with and slidable directly upon and along said drum, guide rods carried by said collar, and grinding units suspended from said guide rods and being revolvable with and movable along said drum.

14. In combination, a support formed for suspension from a crank pin in line with the crank pin axis, a smooth cylindrical drum rotatable upon said support and being fixed against movement along said axis, a collar rotatable with and slidable along said drum, guide rods carried by said collar, grinding units suspended from said guide rods and being revolvable with and slidable directly upon and along said drum, and means cooperable with said support for moving said collar and said units along said axis when said drum and collar are rotated.

15. In combination, a support formed for suspension from an object tov be ground, a drum rotatable `upon said support, means for positively preventing axial displacement of said drum, a guide element slidable upon and rotatable with said drum, grinding wheels carried by said guide element and being revolvable about the axis of said drum, and means operable by thegrinding action of said wheels and coacting directly with said element for advancing the same along said drum. Y

16. In combination, a support formed for suspension from an object to be ground and having a feed screw extending along its axis, a member rotatable about said axis but xed against movement therealong, a guide element rotatable with and slidable upon said member, grinding wheels carried by said element, `and means cooperable with said screw independently of said 1 -ber rotatable about said axis but xed against movement along said screw, a guide element rotatable with and slidable upon said member, grinding Wheels carried by said element, means cooperable with said screw independently of said i member to move said Wheels and said element along said axis and said member, and means for leffecting swinging .adjustment Vof said wheels toward and away from said axis..

18. In combination, a feed shaft attachable to a crank' pin, a tubular support embracing said shaft and having a socket embracing the crank pin end, said shaft having a threaded portion extending beyond said support, a drum rotatable upon but xed against movement along said support, a collar slidable along said drum, brackets suspended from said collar, guide rods carried Aby said brackets and extending along said drum,

grinder units suspended from said rods on opposite sides of the crank pin and being slidable along said drum, and means cooperable with said threaded shaft extension to move said grinder units longitudinally of the crank pin axis 'andof said drum.r Y

19. In combination, a tubular support attachable to the overhanging end of a crank pin and having a threaded extension projecting therebe- Yyond, a drum rotatable upon but iixed against movement along said support, a collar` slidable along said drum and being rotatable therewith,

a bracket suspended from said collar, a guide rod carried by said bracket and being revolvable about the axis of said drum, a grinder unit suspended from said guide rod and being slidable along said drum, and means directly connecting said guide rod and said threaded extension for moving said grinder unitv longitudinally of the drum andgcrank pin axis during rotation of said drum.

20. In combination, a tubular support attachable to the overhanging endrof a crank pin and having a threaded extension, arotary drum journalled on said support, a collar slidable along said drum, brackets suspended from said collar, par- 

